sten gun
The STEN (or Sten gun) was a family of blowback operated, open bolt 9×19mm submachine guns, used by British and Commonwealth forces throughout World War II since 1941 and the Korean War. They were notable for having a simple design and very low production cost, making them effective insurgency weapons for resistance groups. Sten's overall appearance resembles a metal tube with a side-mounted magazine insertion on the left side.
The acronym "STEN" originated from the names of the weapon's chief designers - Major Reginald V. Shepherd, Harold Turpin and Enfield. Sten guns were produced in several basic marks, one of the most common one is the Mk II.